The present invention relates generally to the field of optical imaging. Specifically, the present invention relates to imaging systems for use in detecting microarrays.
Light microscopes provide a powerful tool for investigating samples at submicron resolution. For example, in biology and medicine, appropriate molecular tags, such as fluorescent and immunofluorescent tags, are used to label individual molecules and unique signals from the tags are detected by light microscope to identify their presence. Detection at submicron resolution allows not only determination of the presence of tagged molecules; but also their location in and around cells or tissues.
Two conflicting goals of light microscopy inspection systems concern providing high speed imaging and high resolution imaging. Typically, the resolution of a light microscope is inversely proportional to the imaging speed. Thus, greater resolution is often achieved at the cost of lower inspection rate. One technique to accommodate the aforementioned conflict is to selectively choose the resolution of the system according to specifics of the sample being observed or other conditions of the experiment. Thus, one can use lower resolution to achieve higher speeds while searching for an area of interest in a sample and then once a location of interest is found, imaging can be carried out at higher resolution, albeit at the cost of increasing the time of acquisition for the image.
Significant advances have been made in the ability of microscopes to investigate samples in three dimensions. The advent of confocal microscopes and improvements gained through related technology, allow a discrete point in 3-dimensional space to be detected at high resolution while rejecting unwanted signal from the volume around that point. Scanning confocal microscopy can be carried out to effectively move the point of detection through the sample and collect signal from each point to reconstruct an accurate 3-dimensional image of the sample.
Technology developed for light microscopy has been applied to other fields of image detection as well. For example, the technology has been used to obtain images of microarrays containing thousands of molecular probes attached to the surface of a substrate. Imaging of the surface of the microarrays after exposure to a biological sample of interest allows thousands of target molecules to be evaluated simultaneously, thereby providing vast amounts of information about the sample. For example, microarrays can be used to determine the number and types of genes that are expressed under particular conditions, which can in turn provide a holistic view of the biological response to the condition. Furthermore, similarities and differences between the genetic make-up of individuals can be evaluated using microarrays such that the genetic basis for particular traits can be determined. Information about the gene expression responses and genetic make-up of individuals can be used for diagnostic and prognostic purposes, for example, to determine susceptibility to a certain disease or response to a particular drug.
Although microarray detection has benefited from advances in light microscopy, there are a number of areas that have not been addressed adequately in regard to microarray imaging. In particular, advances directed to increasing image resolution and collection efficiency in light microscopy have come about by improving 3-dimensional confocal detection and altering magnification levels. However, typically array detection is carried out in only 2-dimensions and at a fixed magnification level. Furthermore, many of the advances in high resolution light microscopy have favored improvements in resolution over scan speed. These advances are favorable for imaging small samples, on the order of one or a few biological cells; however, the advances have not necessarily benefited high resolution scanning of substantially larger samples such as microarrays.
Thus, there exists a need for scanning devices and methods that allow imaging of microarrays and other 2-dimensional substrates at high resolution and at high speed. The present invention satisfies this need and provides other advantages as well.